The specific aims of this proposal are to evaluate the predictive value corneal topography derived indices and first surface wavefront aberrations have on selected clinical outcome measures, patient reported symptoms and incident penetrating keratoplasty. The proposed analysis will use data collected on the 1,209 patients enrolled in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study, a multi-center (16 clinics), observational study funded by the National Eye Institute that characterized the prognosis in keratoconus and its impact on quality of life. The proposed project will analyze data collected from the baseline examination and eight annual follow-up visits. This represents a unique opportunity to provide information to clinicians that could alter the treatment of patients with keratoconus. The specific aims of this proposal are: 1) to determine if the short term change (slope) of corneal topography indices are predictive of loss of best corrected visual acuity, manifest refraction visual acuity, contact lens comfort, contact lens wearing period, and NEI-VFQ values 5 to 8 years in the future; 2) to determine the predictive value of topographic indices and wavefront error towards the incidence of penetrating keratoplasty in patients with keratoconus; and 3) to determine if Zernike polynomials or Fourier polynomials derived from first corneal surface wavefront error are superior to commonly used topographic indices for characterizing the corneal surface in eyes with keratoconus. This proposal seeks to use the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study data set to determine if short term changes in complex corneal surface information can predict longer term changes of the cornea. This project will also determine whether this corneal surface data, or changes in this data, can predict when a patient will need a corneal transplant. Lastly, we will attempt to determine if newly applied complex polynomial equations provide more information about the surface than the methods commonly applied today. [unreadable] [unreadable] [unreadable] [unreadable]